I square it with she decided to leave our society, reject our values and join a banned group even if she hasnt broken any laws as she was a minor at the time. i'm not confused at all. she shouldnt be let back in.
I presume you know you have laws in the UK. Which one would you use to prevent her re-entering, given you feel she has not broken any? Or should she be banned purely because you say so?
PS “our values” - bit arrogant of you to assume you speak on behalf of a nation. I’m sure many people have different values to you.